T3 autoantibodies (THAAbs) causing high FT3 test results found by anyone?

[ListentoLearn]

I have been having extremely high FT3 test results without signs or symptoms of over-medication even at 15 hrs post dose. I am on T3 monotherapy. Anyone in a similar situation that found high T3 autoantibodies were causing an artifact with FT3 testing?

[SlowDragon Administrator]

How much T3 are you taking

What are your most recent vitamin D, folate, ferritin, B12 results and ranges

What vitamin supplements are you taking

[ListentoLearn in reply to SlowDragon]

My tested levels of recommended vitamins and minerals are well placed within the ranges recommended by this forum. I supplement heme iron, zinc, selenium, B complex, Vit K2, Vit D3, and Vit C. I am taking ~100 mcg/day split in 4 equal doses. I have no indications of over-medication and feel good. Has anyone had an issue with their FT3 testing artificially high due to FT3 autoantibodies interfering with the immunoassay used in the FT3 test protocol?

A reference paper on FT3 test interference is available at this link:

pubmed.ncbi.nlm.nih.gov/333...

[SlowDragon Administrator in reply to ListentoLearn]

well 100mcg T3 is approximately 40mcg higher than typical daily dose

Suggest you try reducing by 5mcg per day

Wait 6-8 weeks and retest

Then if FT3 is still high reduce by further 5mcg per day

Retest again……etc

[radd]

ListentoLearn,

Welcome to our forum,

TFT's can suffer all sorts of assay interference. The main ones being biotin, macro-TSH, antistreptavidin antibodies, anti-ruthenium antibodies, heterophilic antibodies and yes, thyroid autoantibodies.

Have you been in touch with the lab to see if others have complained. Of course it could be an individual tendency, and we usually suggest unusual results are retested at another lab.

[Capella1 in reply to radd]

wot does it do?

[radd in reply to Capella1]

Capella1

Assay inference means the test is compromised. Macro- TSH used to be common interference, now it seems to be more biotin. I had a raised TSH result once when supplementing biotin. Handy if you are reliant upon a TSH obsessed GP 😉(which I wasn't).

[Capella1 in reply to radd]

I take biotin wot is macho-tsh please.

[radd in reply to Capella1]

Capella1,

It's like TSH with autoimmune antibodies (I think). Latest tests are better at distinguishing between macro and free TSH, and not cross reacting.

There's even mouse dropping assay interference!

[Capella1 in reply to radd]

😲

[ListentoLearn in reply to radd]

Other than biotin in a B complex supplement which I stop 5 days before any test, I am not aware of anything I am taking which could cause the interference. I can do a lab comparison to rule out some assay problem. The levels are so high -- 3x over the top of the FT3 range -- that if real I would have expected some blood pressure, pulse or temperature sign, or a variety of hyper symptoms. Ooooo the mouse interference I hopeth not!

[radd in reply to ListentoLearn]

ListentoLearn,

It can be literally anything, eg contact with pets, immunisations, certain medical treatments, etc. The body is so complex the interconnections and responses are infinite.

[SlowDragon Administrator]

we have other members on (relatively) high doses of T3

Some have found they can/need to reduce dose over time

 DippyDame or  greygoose might pop along and comment

[greygoose in reply to SlowDragon]

I can't really comment because I don't do blood tests. But, at one time, I was on 225 mcg T3. Came down to 75 and was happily on that for several years. But, lately I've found that I'm best on 62.5 and I've been taking that for the past few weeks. So, yes, I have found the need to reduce over time.

[ListentoLearn in reply to greygoose]

The goal for sure is the lowest dose which eliminates symptoms. It has definitely been very slow going to reduce. I had been able to distinguish between FT3 levels a few hours after a dose to levels 15 hours after a dose. Not so confident in these tests at this time.

[DippyDame]

How much T3 are you taking?

What are your FT3 labs.....result plus ref range.

I no longer test....I monitor by signs and symptoms instead.

I self medicate and have a form of thyroid hormone resistance

Highest dose was 212.5mcg, eventually ( about 3 years later) titrated down to 100mcg and just recently dropped to 75mcg......work in progress.

I'm guessing some of the formerly dormant T3 receptors have been stimulated to function again by the supraphysiological doses....hence need for less T3

We are all different so this is just my experience!

[ListentoLearn in reply to DippyDame]

During the past 3 months my FT3 test results are turning up at 11.3 pg/ml and 14.1 pg/ml from the same lab which uses a FT3 test range of 2.0 to 4.4 pg/ml. Prior to that, since last spring, I had been running 3.3-4.2 pg/ml always ~15 hrs post dose. Oddly last September when I did a one off experiment and had the blood draw done 3 hrs post dose, I got a13.2 pg/ml test result. (The next test I did at 15 hrs post dose was 4.2 pg/ml, right back again where my tests normally run.) My functional medical doc is about to start a series of tests to try to determine the cause of the anomaly with the FT3 tests. I have been trying to reduce my dose but I had expected to rely on FT3 tests to monitor my levels -- which seems impractical at the moment!

[trevg in reply to DippyDame]

This is what Paul Robinson advises as RT3 gets reduced by T3 over time.RT3 is a form of auto-antibody to unutilised T4 build up in my book.

I take only ~30mcg in 4 doses daily and T3 top of range around 6. It as been 10 in the past. I hate to think what the high reported doses here would drive my FT3 up to.

[DippyDame in reply to trevg]

I think there is some confusion here about the roles of T4, T3 and rT3

rT3 is produced from excess T4, it is inert and will only remains in the body for about 2 hours before being converted to T2 and eventually excreted

There are many reasons for high rT3 ( other than excess T4) but with it's short life it is not thought to be a problem....the precise meaning and significance of rT3 are still being unpicked

It's worth remembering that FT3 is the measurement at serum level. T3 remains inactive there until it is then transported to the nuclei of the cells where it attaches to T3 receptors and becomes active.

There is no way to measure cellular T3....and this will vary in different tissues in any case.

It is, however, the cellular level of T3 that is important but thankfully for most people there is no problem with the transfer from serum to cells.

However there is a cohort who have a form of Thyroid Hormone Resistance ( I am one) where this is impaired.

To overcome this resistance supraphysiological doses are required to achieve adequate cellular T3....does which would be dangerous for those without RTH

So, your concern about what would happen to you if you took " high reported doses of T3" are well founded....unless you were to be confident that RTH exists

The dose I take would be potentialy dangerous for non RTH patients! I'm assuming this is what you refer to as, " high reported doses"

As for rT3, results from long, expensive tests are unlikely to give us any useful information regarding thyroid treatment because it is inert.

30mcg T3 is not an excessive dose and so long as your labs remain within the reference range you can conclude that you are not overmedicated.

[trevg in reply to DippyDame]

I keep T3 intake low and tolerate falling asleep a lot during the day. Currently looking into low Vit B12 level as an added cause, via Pernicious anemia. This is very like Thyroid issue in presentation and low level of treatment.

Also, yet another autoimmune possibility to add to three others..

PS: I always understood RT3 to be fairly constant, once established and only exercise or T3 taken would reduce. Paul Robinson, I think!

[tcpace in reply to DippyDame]

As a matter of interest DD, how can anyone who is "T3 only" tell if they are THR and hence whether they may need to try a substantial increase in dose for a while to get the cellular T3 receptors working properly? My wife, who is currently on 60-70mcg T3 daily, doesn't feel as if it's enough but she's reluctant to go higher in case it causes problems. You and Greygoose must have gone through a similar phase to get to a daily dose of 200+mcg. Just wondering whether you were hesitant about doing so.

[DippyDame in reply to tcpace]

My bio may help.

Listening to the body and being aware of all signs and symptoms is essential because there are no blood tests to monitor dose.

It is the very last resort after every other possible dosing route has been explored...not to be taken lightly!

Of course I was hesitant to start the journey and read a great deal before making the decision but after much serious consideration concluded it was my final option.

I also understood that if signs and symptoms of overmedication arose I could just drop my dose back down

I'm now fairly certain I've had this problem all my life and looking back into my medical history the signs are there. I'm also fairly certain both my mother and my maternal grandmother had some form of RTH.

Another thing that may help is this excellent ebook which is available on Amazon for £3.56 or free if you have Amazon Prime. It is called "Impaired Sensitivity to Thyroid Hormone (Thyroid Hormone Resistance)" by Hugh A Hamilton

I'm not a medic and not in a position to advise....I can only offer my own experience involving a process of elimination and trial and error....and much, much reading!

But, in your wife's shoes I might try adding another 5 or 6.25mcg ( a quarter of a 20mcg or 25mcg tablet) and see if that helps....

Wishing her well

DD

[samaja]

For some people it takes more than 15 hours to test within range. I usually test at 18 and i know some people test after 24 h. I gather you probably test at the same time and these high results are recent but if you feel well and and your signs and symptoms are good I wouldn't pay much attemtion to tests alone.

[trevg]

I'm on T3 only some years now, with a mid 2022 level of 7.3 pmol/L (3.8 - 6.0) -which I keep as a wkg max- due to high S.H. Binding Globulin reading.

I only use a relatively low 35mcg T3 daily, in 4 split doses.

I may need more T3 however, as I've tended to bite my tongue a lot lately & have a lot of napping in the day, which were a hypo markers - before T3 treatment.

I do wonder about 'T3 pooling' raised in chat. I think that was both T4 with T3 though.?

Does pooling occur with T3 only and can higher dose Lithium help to reduce any remaining RT3 -along with Selenium, as reported recently?

[tattybogle in reply to trevg]

trevg ~ re. your question on 'pooling'

healthunlocked.com/thyroidu.... pooling-an-outdated-concept-list-of-useful-posts-which-explain-why-reverse-t3-blocking-t3-receptors-is-not-a-thing-.

[trevg in reply to tattybogle]

There's still a lot of varied opinion there. I never got the idea of T3 pooling anywhere , simply that it had to compete with RT3 hanging on a thread and blocking uptake. This may well be wrong but the case was never shown clearly by STTM in the first place so the longevity of RT3 is the arbiter and it doesn't seem to move much but my testing is infrequent. This is another casualty of NHS 'no test RT3' policy, blocking info that could help patients. I've always had to pay for tests refused.